无子西瓜的培育过程如下列简图所示:根据上述图解,结合你所学过的生物学知识,下列叙述中

题型:单项选择题

问题:

无子西瓜的培育过程如下列简图所示:

根据上述图解,结合你所学过的生物学知识,下列叙述中正确的是()

A.①过程只能用秋水仙素处理,其作用主要是抑制细胞有丝分裂前期纺锤体的形成

B.由三倍体种子发育成无子西瓜,与中心体有密切的关系

C.三倍体植株所结的植株的

D.四倍体植株所结的西瓜,果皮细胞内含有4个染色体组

考点:高中生物染色体变异与育种染色体变异与育种题库
题型:单项选择题

补偿电容器组与电机直接连接,保护和控制装置共用一套,一起投切,这种补偿方式叫()。

A.随机补偿

B.电动机补偿

C.保护补偿

D.控制补偿

题型:单项选择题

(5分)某班学生用乒乓球模拟生殖细胞来探究生男生女的概率问题,实验步骤如下:

①甲桶中装入60个黄球,乙桶中装入白球与黄球各30个,分别摇匀。②分别从甲乙两桶中随机抓取一个球,组合在一起,记下两球的组合(黄球与黄球组合用A表示,黄球与白球组合用B表示)。将抓取的乒乓球放回原桶,摇匀。③重复②步骤50次。全班共分7个小组,实验记录结果如下表:

组合

组别

1234567
A(黄球与黄球组合)24272521283019
B(黄球与白球组合)26232529222031
(1)白球模拟的生殖细胞是         ( 填“精子”或“卵细胞” )。黄球模拟的生殖细胞中含有        性染色体。

(2)为了使实验更准确可靠,应如何处理以上数据                       

(3)从实验数据分析,得出的实验结论是:生男生女的机会                

(4)有些人为了满足生男或生女的愿望,怀孕期间请医生对胎儿进行性别鉴定,决定取舍。这种做法对吗?                 。

题型:单项选择题

阅读理解。

     During my elementary school years, I used to compare my mom with my best friend Tiffany's mom.

     Tiffany's mom always gave her lots of money to buy the most fashionable clothes and favorite food.

Her mom allowed her to do anything she liked. I really admired Tiffany. My mom didn't give me much

pocket money and she always told me that I should behave myself. I was annoyed with her.

     Whenever I didn't get what I wanted, I would complain to my mom, Tiffany's mom would give her

that! I wish she were my mom. Every time, my mom would calmly say "Poor Tiffany". I couldn't

understand her. "She shouldn't be feeling sorry for Tiffany!" I thought, "She should be feeling sorry for

me."

     One day, I couldn't help saying to Mom, "Poor Tiffany? Lucky Tiffany! She gets everything she

wants! Why do you feel sorry for her?" I burst into tears.

     My mom sat down next to me and said softly, "Yes, I do feel sorry for her. I have been teaching you

a lesson that she will never be taught."

     I looked up at her, "What are you talking about?"

     Mom said with care, "One day she will really want something. Maybe she'll find out that she can't

have it. Her mother won't always be around to give her money, and what's more, money can't buy

everything."

     She continued, "I have taught you valuable lessons by not giving you everything you want. You'll

know how to look for bargains and save money, but she won't. You'll understand that you need to

work hard to get the things that you want but she won't. When Tiffany is a grown woman, she'll wake

up one day and she will be wishing that she had a mom like the one you've got. Life lessons are more

important than modern clothes and delicious food."

     It took some time, but I eventually understood my mom's words. Now I am a happy and successful

woman. 

1. During the author's elementary school years, she __________.

A. wished that her mom were as good as Tiffany's

B. went to school with Tiffany every day

C. usually compared her lesson with Tiffany's

D. sometimes gave lots of money to Tiffany 

2. Why did the author's mom always say "Poor Tiffany"?

A. She felt sorry for Tiffany because Tiffany was poor.

B. She wanted to tell a lie to comfort the author.

C. She thought that Tiffany was spoiled by her mother.

D. She told the author this and wanted her to help Tiffany.

3. What do we learn about the author's mother?

A. She was strict and taught the author to be independent.

B. She cared for other people's children more than her own.

C. She thought that life lessons were as important as money.

D. She was so poor that she couldn't give the author much money.

4. What can we infer from the passage?

A. The author was quite annoyed with her mother in the past.

B. The author's mother felt sorry for Tiffany.

C. Tiffany's mother took the author's mother's advice.

D. The author is thankful to her mother now.

题型:单项选择题

接触式测温仪表分为哪几类?

题型:单项选择题

一事物成为自身并区别于其他事物的是()

A、量

B、度

C、质

D、关节点

更多题库